In general, Divine Command Theory (DCT) says that “If God commands X, then X is a moral obligation for us.” I will limit my discussion of DCT to moral obligations and prohibitions, which are used synonymously with rightness and wrongness. These are deontic properties which is distinct from goodness, which is axiological. For example, something can be good to do, such as becoming a lifeguard to save lives, but we do not have a moral obligation to do so. So I will use DCT as a theory of rightness that presupposes a theory of the good.

The Euthyphro Dilemma (ED) is often raised against DCT. For example, in the case of rape Walter Sinnott-Armstrong asks, “Did God have any reason to command this? If not, his command was arbitrary, and then it can’t make anything morally wrong. On the other hand, if God did have a reason to command us not to rape, then that reason is what makes rape morally wrong. The command itself is superfluous. Either way, morality cannot depend on God’s commands.” In short, the ED says:

Either

(1) God has no reasons for His commands,

or

(2) God has reasons for His commands but these reasons are sufficient by themselves in explaining moral obligations.

Embracing (1) leads to objections such as God’s commands being arbitrary which makes morality arbitrary. Furthermore, this means that God’s commands could possibly be what we consider abhorrent, such as commanding that we ought to torture babies solely for fun resulting in a moral obligation to do so. Any objection to this that says God has reasons is a move away from (1).

Embracing (2), shows that actions are morally obligatory prior to and independent of God’s commands, making God at most an epistemic authority who is just conveying His perfect moral knowledge to us. However DCT proponents want God’s commands to explain moral obligations instead.

From the ED, I think a third option is clear, which DCT proponents can well affirm:

(3) God has reasons for His commands but these reasons are not sufficient by themselves in explaining moral obligations without God’s commands.

God just needs good reasons to make an act morally obligatory. An act itself does not have the property of being morally obligatory prior to God’s command, but can have other relevant properties, such as being morally good or even “non-moral considerations ultimately based in God’s nature.” God’s commanding however adds certain properties that make the act obligatory. To use an analogy, let us think of other obligations. Consider a legal obligation not to smoke in a certain area when implemented by law. For the obligation to arise, there must be good reasons behind why it is implemented by law. Yet those reasons by themselves are not sufficient to give us legal obligations unless it is actually implemented by law. Hence a legal obligation arises because it is implemented by the law and there are good reasons for it being implemented. Likewise, DCT proponents say that a moral obligation arises because it is commanded by God and God has good reasons to command it.

One objection to (3) is based on a principle that moral properties strongly supervene on non-moral properties necessarily. Matthew Jordan says, “The doctrine of global moral supervenience, the uncontroversial thesis that any two possible worlds that are identical in all non-moral respects must be identical in all moral respects, implies that moral truths – at least the most fundamental ones – are metaphysically necessary.” So moral obligations are in some way determined and fixed by their non-moral properties. How exactly does moral supervenience amount to an objection to (3) exactly?

In “An Essay on Divine Authority”, Mark C. Murphy argues that DCT “must be false, for it, in conjunction with a very weak and plausible claim about God's freedom in commanding, entails that the moral does not supervene on the non-moral.” To show this, he argues that according to voluntaristic versions of DCT, where God is free to choose what to command, there can be two possible worlds exactly the same in their natural features, but God gives different commands and thus we have different moral obligations in two possible worlds that have the same natural features. This seems to violate the supervenience of the moral on the non-moral, since two worlds with the same natural features should have the same moral obligations.

How may a proponent of a voluntaristic version of DCT reply? C. Stephen Evans points out that for the theist, non-moral properties can include both natural and supernatural properties. Supernatural properties are “properties possessed because what has the properties has a certain kind of relation to God,” such as “being commanded by God”, “being preferred by God,” or “being pleasing to God” or “being conducive to a better relation to God.” If an act is commanded by God, then it will have the further properties mentioned, such as “being conducive to a better relation to God” which is a non-moral property. These non-moral properties may even be linked to natural properties such as “being conducive to the agent’s happiness.” If a relationship with God is conducive to our happiness, and such a relationship requires that we follow what He commands, then the property of “being commanded by God” would be one that could alter the moral status of an act, especially for those who think that the moral status of an act is linked to whether the act is conducive to an agent’s happiness. Hence on DCT, it is both natural and supernatural properties that make up non-moral properties which moral properties supervene on. If so, then there can be two worlds alike in all their natural properties but differ in their supernatural properties, and hence moral properties can be different as it supervenes on both. So moral supervenience along with God’s freedom does not amount to an objection against (3).